Current computing environments typically include a graphical user interface (GUI). IBM personal computers and IBM compatibles run either OS/2 or Windows. The Macintosh has always had GUI capabilities as part of its operating system. Even higher end computers, including those that run Unix or VAX/VMS operating systems, are available with components that provide a GUI environment.
GUI's are generated using a set of software tools that put graphical objects on the computer display. One of these graphical objects is a screen pointer that the user controls with a mouse or a trackball. The user moves the mouse to position the pointer on the screen over selected objects on the screen. The user can select an object by using a selecting device which is typically a mouse switch. By selecting an object, the user instructs the operating system or an application to execute the function associated with the object. The GUI objects can include the graphical representation of buttons, menus or any other graphic object.
GUI's are the foundation of hypertext and hypermedia applications. Such applications allow computer users to create interfaces in which graphical objects are configured to correspond, or to link to objects of information. For example, a user may create an interface having the graphical representation of a button to display a motion video by selecting the button with a screen pointer. Similarly, the button can be configured to make a sound, display an image or display a separate text file.
Today's increasing interest in the Internet is due in part to the improvements in hypermedia applications. The World Wide Web is growing dramatically due to the evolution of standard markup languages that allow users to mark documents with links to other documents, and of presenters or viewers that interpret the markup language in the documents allowing the users to view the links.
One of the first markup tools was the Standard Generalized Markup Language (SGML). SGML was developed by the International Standards Organization and has been adopted by the Department of Defense and other government agencies as a way of standardizing documentation. SGML is machine-based in a manner similar to a computer language. An SGML Document Type Definition (DTD) may be defined according to the specifications of SGML for a given document structure. The DTD defines elements to be embedded in a document. The documents are then viewed using a viewer or browser that interprets the elements in the document according to the data structure defined in the DTD.
The HyperText Markup Language (HTML) is an instance of a DTD defined by SGML. HTML elements or codes are embedded into documents for use with HTML browsers. Browsers display the documents according to stylesheets associated with the embedded codes. The stylesheets contain rules or instructions that dictate the appearance of a document as presented by a browser. Stylesheets may also contain references to other documents in different computers. These references may be used in conjunction with context-sensitive regions of the documents such that a user retrieves the document reference by selecting the region. In this manner, an author links one document to others in a meaningful way such that a viewer may provide a user with access to information in documents that are linked together in a web-like fashion.
One common characteristic of many browsers is that the links to information are presented solely within documents. The links may take the user to other documents or to locations within the same document, but typically, the elements that provide the link control are within the documents.
Having the control to the information links within the documents themselves is adequate where the documents are short and where the purpose is to obtain information in brief, concise statements. But where a document is long, it becomes difficult to browse the document since the only potential access to other destinations are in whatever part of the document is currently being displayed.
Moreover, organizations often work with standardized documents. These documents typically have a carefully defined purpose and are usually characterized by a standard structure. These documents may be long and the main purpose for viewing the documents is often to access information found in a specific section of the well-known structure of the document.